Many types of textile processing equipment, such as carding machines and airlay web formers, are designed to receive textile fiber from a bale in the form of a batt wherein the batt is formed of a collection of tufts of fiber. In the operation of such textile equipment, the tufts are conventionally pulled or taken whole into the textile equipment. Exceptionally large tufts may overload the textile equipment by providing too much fiber at once. Thus, it is preferred that the batts are formed with smaller tufts therein and the feed rates are set to accommodate the largest remaining tufts. In addition, bale opening equipment and perhaps other equipment are used to open the bales of fiber and break the tufts into smaller clumps of fiber to facilitate less overloading of equipment and higher feed rates.
To better appreciate certain aspects of the present invention, a common understanding or definition of the word "tuft" is provided in U.S. Pat. No. 5,606,776 to Freund et al. (hereafter, Freund) assigned to DuPont. In any event, it should be understood that the tufts are rather light, soft, readily deformable and tend to move with and be very reactive to any flow of air in their vicinity.
As noted above, the feed rates of carding equipment and airlay web formers are limited by the size of the largest tufts in the batt. The batts are typically formed by chute feeders which are designed to form a batt f preferably uniform thickness and density. Such chute feeders simply stack the tufts of fiber in a channel having a width approximately that of the carding machine and a thickness of approximately the thickness of the batt. Examples of conventional chute feeders are provided in a number of issued U.S. patents, such as U.S. Pat. Nos. 3,738,476; 4,154,485; 4,449,272; 4,930,190; and 5,157,809. Another example is Freund, mentioned above, which describes an apparatus for removing fiber from bales to form a batt of uniformly distributed fiber that is fed to a web forming mechanism and wherein the apparatus incorporates a chute feeder.
One of the difficulties in handling cut textile fiber is the tendency for fiber in the bin portion of the chute feeder to settle in mounds or piles when it is desirable that the fiber be generally uniformly dispersed. It is a problem whether the fiber is present as individualized fiber filaments, or in clumps, tufts or the like and especially combinations thereof. Non-uniform webs are often formed as a result of the non-uniform distribution in the fiber bed at the inlet side of the chute feeder. The mounds of fiber in the bin cause heavier or denser loaded areas in the batt that correspond generally to the mounds. The denser and heavier portions can be found throughout the process and the effect is observed in the final product by variation in basis weight, particularly in the cross-machine direction.
There have been various approaches to addressing this problem. For example, U.S. application Ser. No. 09/163,679 filed Sep. 30, 1998 and assigned to DuPont is directed to control of the fiber delivery by using several different flow paths to provide a number of small mounds rather than a single large mound. Even though this provides some improvement in the uniformity of the batt, it has been found that further improvement can be made by controlling the flow of the air stream that transports the fiber.